The present invention relates to a substrate delivery method for transferring or receiving a substrate to or from a substrate holder mechanism (a top ring) serving to hold the substrate to perform a polishing operation in a substrate polishing apparatus for polishing a substrate such as a semiconductor wafer, and relates also to a substrate delivery mechanism for transferring or receiving the substrate to or from the top ring as well as a substrate polishing apparatus comprising the substrate delivery mechanism.
This type of substrate delivery mechanism according to a prior art typically comprises a pusher mechanism for transferring or receiving a substrate to or from a top ring, in which when the pusher mechanism is to receive the substrate from the top ring, a gas (including air and the like) or a liquid (including purified water and the like) or any mixture thereof is injected from a substrate holding surface of the top ring, so that the substrate may detach from the substrate holding surface and drop onto a substrate retaining section of the pusher mechanism disposed thereunder. In such a method allowing for fluid to be injected from the substrate holding surface of the top ring, however, if the substrate holding surface of the top ring is firmly sticking to the substrate, the fluid from the substrate holding surface must be injected for a longer period sufficient to detach the substrate therefrom, leading to a lower throughput of the substrate in the apparatus.
FIGS. 1(a) and 1(b) show an exemplary configuration for the substrate delivery mechanism in the prior art, wherein FIG. 1(a) shows a mode immediately before a substrate is transferred to a substrate tray of a pusher mechanism. FIG. 1(b) shows a mode of a substrate which has dropped into a substrate tray of a pusher mechanism. In FIGS. 1(a) and 1(b), reference numeral 101 designates a top ring having a plurality of through-holes 106 formed in a substrate holding surface 104, the plurality of through-holes 106 being in communication with a chamber 107 which is connected to a pressurizing/exhausting source (though not shown) for supplying/exhausting a gas, a liquid or a mixture thereof to/from the chamber via a pipe 108.
Reference numeral 102 designates a pusher mechanism, which comprises a main shaft 110 by which a ring-like top ring guide 109 is supported via a centering mechanism 111 and a spring 112. Reference numeral 105 designates a ring-like substrate tray disposed on an inner side of the top ring guide 109 and the substrate tray 105 is adapted to be lifted-up by a substrate lifting table 113 supported on a top end of the main shaft 110. When the main shaft 110 is lifted-up by a cylinder, though not shown, the top ring guide 109 is, as shown in FIG. 1(a) and FIG. 1(b), brought into contact with an outer periphery and an under surface of the top ring 101. Under this condition, there is a clearance “a” provided between the substrate holding surface 104 of the top ring 101 and a substrate carrier surface of the substrate tray 105.
To transfer a substrate “Wf”, held on the substrate holding surface 104 of the top ring 101, onto the substrate tray 105, starting from the mode shown in FIG. 1(a), a fluid (a gas, a liquid or a mixture thereof) 114 is injected from the plurality of through-holes 106 formed in the substrate holding surface 104 by supplying the fluid 114 to the chamber 107 of the top ring 101 from the pressurizing/exhausting source(not shown) through the pipe 108 to thereby detach the substrate Wf from the substrate holding surface 104 so as to be dropped into the substrate tray 105, as shown in the mode of FIG. 1(b). On the other hand, when the wafer Wf is to be held by the top ring 101, starting from the mode shown in FIG. 1(b), the main shaft 110 of the pusher mechanism 102 is moved up such that the substrate tray 105 may be lifted up by a distance equivalent to the clearance “a” to bring the substrate Wf carried thereon into contact with the substrate holding surface 104 of the top ring 101, and then the chamber 107 is exhausted by the pressurizing/exhausting source via the pipe 108 so as to vacuum-chuck the substrate Wf onto the substrate holding surface 104.
Although a number of times as well as a period of injection of the fluid 114 can be set arbitrarily for detaching the substrate WF from the top ring 101, which has been held thereby, the substrate Wf may occasionally adhere tightly to the substrate holding surface 104 depending on a polishing condition of the wafer and/or characteristics of the top ring 101. Especially, in a case of employing an elastic member made of rubber or the like on the substrate holding surface 104, the substrate is more likely to stick to that elastic member. In this case, in order to transfer the substrate Wf from the top ring 101 to the substrate tray 105 in a stable manner, a longer period of injection of the fluid 114 may be required. This may problematically increase substrate transfer time, which will be one factor in decreasing a processing rate in the apparatus.